1. Field of the Invention
The present invention relates to a semiconductor device in which an optical transmission medium and a light-receiving element carrying out photoelectric conversion are mixed and mounted, and more particularly, to an optoelectronic device comprising a two-dimensional optical waveguide as an optical transmission medium. The present invention further relates to an optoelectronic wiring substrate comprising an electric wiring layer and an optical transmission layer. Furthermore, the present invention relates to a spherical device.
2. Related Background Art
For cellular phones and personal digital assistants (PDA) which are spreading at a remarkable pace in recent years, there are demands that these devices be smaller, lighter and provided with transistors capable of extremely high-speed processing.
It has been pointed out that as the processing speed of transistors increases, or as the clock frequency of the CPU increases, the influence of transmission delay in the electronic circuit substrate also increases. Since the transmission delay is proportional to a product of a wiring resistance by a wiring capacitance, it is necessary to reduce the wiring resistance or the wiring capacitance. The simplest way to prevent the transmission delay is to minimize a wiring distance within each chip or between chips.
On the other hand, the processing speed is expected to improve as the wiring distance becomes shorter, but another problem becomes apparent. That is the problem of EMI (ElectroMagnetic Interference). Since electronic parts are placed closer to each other, a wiring distance becomes shorter but a wiring density becomes higher. As a result, when high-speed signals flow through adjacent signal lines, mutual electromagnetic induction causes electromagnetic waves to interfere with each other and generate noise, making it impossible to transmit signals correctly.
There are an increasing number of cases wherein particular mobile terminals are driven with a larger current than conventional ones under the influence of proceeding devices operation at a lower voltage, thereby raising concern that influences of EMI becomes larger.
A method of using an optical wiring having an inherent advantage of causing no electromagnetic induction is proposed to solve the EMI problem.
For example, Japanese Patent Application Laid-Open No. 2000-235127 discloses a circuit substrate integrating an electronic element and an optical element as shown in FIG. 35. In FIG. 35, reference numeral 5201 denotes an electronic integrated circuit substrate; 5204, a light emitting part; 5206, a light receiving part; 5207, an optical path change section; 5210, a contact electrode. Reference numeral 5211 denotes polyimide to bond the circuit substrate 5201 and the light emitting part or light receiving part. Reference numeral 5212 denotes an electric wiring; 5213, plane light emitting laser; 5214, a photodiode; 5215, a low reflection film; 5216, a polymer layer; 5217, a first clad layer; 5218, a core layer; 5219, a second clad layer; 5220, a high reflection film.
The light emitted from the light emitting part 5213 is reflected by the optical path change section, propagates through the core layer 5218 in the direction indicated by an arrow 5221 in FIG. 35, the light path is changed again and the light is received by the light receiving part 5206. When the propagation direction of the incident light is predetermined, it is possible to replace a part of the electric signal wiring in the configuration shown in the above-described FIG. 35 with an optical wiring.
However, when the incident light that propagates through the core layer 5218 is the light from the direction 5222 indicated by the arrow in FIG. 35, it is impossible for the configuration shown in FIG. 35 to receive the light.